Purification and characterization of phosphoribosylpyrophosphate synthetase from rubber tree latex
Gallois Richard
Purification and characterization of phosphoribosylpyrophosphate synthetase from rubber tree latex - Plant Physiology 1997 - 847-852
Phosphoribosylpyrophosphate synthetase (PRS; EC 2.7.6.1) from Hevea brasiliensis Muell. Arg. latex was located in the cytosol. After purification, its apparent molecular weight under nondenaturing conditions was estimated at 200,000+_ 10,000; a single band at 57,000 +_ 3,000 was detected after sodium dodecyl sulfatepolyacrylamide gel electrophoresis. The enzyme seemed to be a homotetramer. Its affinity constants were estimated at 200 +_ 30 mM for adenosine triphosphate and 40 +_ 2 mM for ribose-5-phosphate. The purified enzyme proved to be functional in a paraphysiological medium (cytosol deproteinized by ultrafiltration). Optimum pH was 7.5 in buffer and 6.5 in a paraphysiological medium. No PRS activity was detected in the absence of the Mg2+ ion. Of the numerous compounds tested, only Mn2+, phosphoribosylpyrophosphate, and inorganic phosphate affected the enzymatic reaction. Mn2+ (inhibitor constant = 20 mM) and phosphoribosylpyrophosphate (inhibitor constant = 30mM) were inhibitors. PRS responded allosterically (Hills coefficient = 2.3) to ribulose-5-phosphate in the presence of a physiological concentration of inorganic phosphate (10mM). These results are set in the physiological context of laticifers.
Phosphoribosylpyrophosphate synthetase
Rubber tree latex
Purification and characterization of phosphoribosylpyrophosphate synthetase from rubber tree latex - Plant Physiology 1997 - 847-852
Phosphoribosylpyrophosphate synthetase (PRS; EC 2.7.6.1) from Hevea brasiliensis Muell. Arg. latex was located in the cytosol. After purification, its apparent molecular weight under nondenaturing conditions was estimated at 200,000+_ 10,000; a single band at 57,000 +_ 3,000 was detected after sodium dodecyl sulfatepolyacrylamide gel electrophoresis. The enzyme seemed to be a homotetramer. Its affinity constants were estimated at 200 +_ 30 mM for adenosine triphosphate and 40 +_ 2 mM for ribose-5-phosphate. The purified enzyme proved to be functional in a paraphysiological medium (cytosol deproteinized by ultrafiltration). Optimum pH was 7.5 in buffer and 6.5 in a paraphysiological medium. No PRS activity was detected in the absence of the Mg2+ ion. Of the numerous compounds tested, only Mn2+, phosphoribosylpyrophosphate, and inorganic phosphate affected the enzymatic reaction. Mn2+ (inhibitor constant = 20 mM) and phosphoribosylpyrophosphate (inhibitor constant = 30mM) were inhibitors. PRS responded allosterically (Hills coefficient = 2.3) to ribulose-5-phosphate in the presence of a physiological concentration of inorganic phosphate (10mM). These results are set in the physiological context of laticifers.
Phosphoribosylpyrophosphate synthetase
Rubber tree latex